This invention relates to a polisher for polishing the end surface of a semiconductor wafer and a polishing head for such a polisher.
Semiconductor wafers are produced by forming insulating films and metallic films which become the wiring on a semiconductor substrate. During the production of such a wafer, the metallic film may roll over its end surface and if such parts become peeled off and start floating, they may end up by getting attached to the wiring structure on the semiconductor substrate. As a result, semiconductor chips obtained by cutting such a semiconductor wafer may not be able to function as designed. Thus, it is necessary to remove such rolling-over parts produced on the end surface of a semiconductor wafer and the polishing of the end surface of a semiconductor wafer has become an important part of the production process for wafers.
Conventionally, the end surface of a semiconductor wafer is polished by affixing a polishing pad around a columnar polishing drum, placing the semiconductor wafer on a holder table, and rotating the drum while pressing the semiconductor wafer placed on the holder table disposed perpendicularly or obliquely, as disclosed, for example, in Japanese Patent Publications Tokkai 1-71656 and 3-208550. With a conventional device of this type, however, the wafer must be turned over and reset on the table after one side is polished such that the other side can be similarly polished because the wafer is positioned perpendicularly or obliquely to the surface of the polishing pad around the polishing drum. This tends to increase the time required for the polishing work.
When the polishing pad of such a prior art polisher is replaced, the polishing drum is dismantled from the polisher first to remove the pad before a new pad is attached around the polishing drum and the drum is then set on the polisher. Such work is both cumbersome and time-consuming.
It is therefore an object of this invention to provide a polisher and a polishing head for polishing the end surface of a semiconductor wafer easily and to make it easier to replace its tool for the polishing. A polishing head embodying this invention may be characterized as comprising a driver roller, a driving means for rotating this driver roller, a pair of upper and lower follower rollers one above the other parallel to and horizontally separated from the driver roller, and an endless polishing belt around the driver roller and the follower rollers. The polishing belt is caused to run as the driver roller is rotated, and the end surface of the semiconductor wafer is pushed against the polishing belt between the upper and lower follower rollers.
A pair of upper and lower tension-controlling rollers is further provided for controlling the tension in the polishing belt between the upper and lower follower rollers. The upper tension-controlling roller serves to push the polishing belt downward between the upper follower roller and the driver roller, and the lower tension-controlling roller serves to push the polishing belt upward between the lower follower roller and the driver roller. At least one of this pair of upper and lower tension-controlling rollers is made movable in the vertical direction such that the belt can be easily removed and a new replacing belt can be set.
The polishing head may be further provided with a contact pad having a removably attached pressure sensor, disposed on the back side of the polishing belt between the pair of upper and lower follower rollers.
A polisher embodying this invention may be characterized as comprising a polishing head as characterized above, holding means for holding and rotating the wafer, and attaching means for attaching this polishing head to the polisher. According to a preferred embodiment, the attaching means comprises a torque motor having a drive shaft penetrating a support shaft and a connector for connecting the drive shaft with the polishing head. The polishing head has a bearing serving to attach an end part of the support shaft to the polishing head such that the upper and lower follower rollers are parallel. The polishing head rotates upward and downward around the support shaft as the torque motor is activated.
The attaching means may also be characterized as comprising a torque motor having a drive shaft that penetrates a support shaft, a crankshaft mechanism connected to the support shaft through a link, and a connector that connects the drive shaft of this motor with the polishing head. The polishing head has a bearing that serves to attach an end part of the support shaft to the polishing head such that the upper and lower follower rollers are parallel. The connector may include a rotary arm affixed to the drive shaft of the torque motor, a sliding arm affixed to the polishing head, a slide mechanism for connecting between the rotary arm and the sliding arm such that the sliding arm can move with respect to the rotary arm parallel to the support shaft and that the polishing head moves reciprocatingly in an axial direction of the support shaft if the crankshaft mechanism is activated. The slide mechanism may comprise a rail having an indented portion and another rail having a protruding portion, these two rails being parallel to each other and engaging to each other by their indented and protruding portions.
If the polishing head has a contact pad as described above, this contact pad may be characterized not only as being disposed on the back side of the polishing belt between the pair of upper and lower follower rollers but also wherein the support shaft is adjusted to a point on the surface of the contact pad facing the polishing belt.
With a polishing head thus structured, or a polisher provided with such a polishing head, it is not necessary to polish each end surface of a wafer at a time and the polishing can be carried out easily in a short time. Moreover, the polishing belt as the tool for the polishing can be exchanged easily and quickly.